1. Field of the Invention
The invention relates to a process for preparing a substrate containing I-125 used to manufacture radioactive I-125 sources. Such radioactive sources are used in devices for measuring bone density in the body, that is, in bone densitometers. Such sources are also used in diagnostic devices such as portable devices for taking X-rays. Furthermore, such sources are used in radiation therapy, as in treating tumors. In radiation therapy, I-125 sources are typically called "seeds." It is important that such I-125 sources contain measured amounts of I-125.
2. Description of the Prior Art
Various ways to deposit I-125 on a substrate are known such as treating very small resin beads, typically 1 to 2 millimeter spheres, or small pieces of wire, typically 1 to 2 millimeters in length with a liquid phase which contains I-125, for example, in the form of a salt. I-125 is thus caused to be deposited from the liquid phase onto the beads or wire which serve as the substrate.
I-125 has also been deposited from a basic liquid solution onto a nylon filament. This procedure is described in more detail in U.S. Pat. No. 3,351,049.
I-125 has also been deposited on a substrate as follows: a silver substrate is chlorided by an electrochemical process, followed by treatment of the chlorided substrate with a basic sodium iodide solution. This process is more fully described in U.S. Pat. No. 4,323,055.
Disadvantages of the above processes for depositing I-125 on substrates include the fact that it is hard to control the amount of I-125 deposited upon a substrate by these above processes, and furthermore, by these above processes, uniform deposition of I-125 over the substrate is not obtainable.
An additional disadvantage of these prior art processes is that it is difficult to handle the substrates, such as the resin beads or pieces of wire or nylon, that are prepared. Because of this difficulty in handling, there exists the potential danger of irradiation to the operator and the further problem of contamination of the I-125 source prepared.